Expandable fusion device for positioning between adjacent vertebral bodies

ABSTRACT

In some embodiments, system and/or method may include an intervertebral implant for a human spine including an upper body, a lower body, first and second expansion members, and an expansion mechanism. A superior surface of the upper body may function to engage a first vertebra of the human spine. An inferior surface of the lower body may function to engage a second vertebra of the human spine. The first expansion member may include at least a first angled portion positionable, during use, between the upper body and the lower body. The second expansion member may include at least a second angled portion positionable, during use, between the upper body and the lower body. An expansion mechanism may convey, during use, the first and second angled portions in opposing directions increasing a separation distance between the upper body and the lower body.

REFERENCE TO PENDING PRIOR PATENT APPLICATIONS

This patent application is a continuation of pending prior U.S. patentapplication Ser. No. 15/351,943, filed Nov. 15, 2016 by Flexuspine, Inc.for EXPANDABLE FUSION DEVICE FOR POSITIONING BETWEEN ADJACENT VERTEBRALBODIES, which in turn is a continuation of prior U.S. patent applicationSer. No. 14/185,561, filed Feb. 20, 2014 by Erik Wagner et al. forEXPANDABLE FUSION DEVICE FOR POSITIONING BETWEEN ADJACENT VERTEBRALBODIES, which claims benefit of prior U.S. Provisional PatentApplication Ser. No. 61/766,982, filed Feb. 20, 2013 by Erik Wagner etal. for EXPANDABLE FUSION DEVICE FOR POSITIONING BETWEEN ADJACENTVERTEBRAL BODIES.

The three (3) above-identified patent applications are herebyincorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates to spinal implant devices and methods forpromoting fusion between adjacent vertebral bodies, and moreparticularly to expandable fusion devices that can be inserted betweenadjacent vertebral bodies to facilitate the fusion thereof.

2. Description of the Relevant Art

The human spine is a complex mechanical structure, composed ofalternating bony vertebrae and fibrocartilaginous discs that areconnected by strong ligaments and supported by musculature, that extendsfrom the skull to the pelvis and provides axial support for the body.

The vertebrae generally comprise a vertebral foramen bounded by theanterior vertebral body and the neural arch. The vertebral bodycomprises two end plates (i.e., superior and inferior) made of thincartilage overlying a thin layer of hard cortical bone that attaches tothe spongy, cancellous interior bone of the vertebral body. The neuralarch consists of two pedicles and two lamina that are unitedposteriorly. The spinous and transverse processes protrude from theneural arch. The superior and inferior articular facets lie at the rootof the transverse processes.

The intervertebral discs primarily serve as a mechanical cushion betweenadjacent vertebral segments of the spinal column and generally comprisetwo basic components: the annulus fibrosis and the nucleus pulposus. Theannulus fibrosis forms the outer perimeter of the disc and is a toughring that binds adjacent vertebrae together. The nucleus pulposus fillsthe interior of the disc and carries load.

The spine as a whole is a highly flexible structure capable of a highdegree of curvature and twist in nearly every direction. However,genetic or developmental irregularities, trauma, chronic stress, anddegenerative wear can result in spinal pathologies for which surgicalintervention may be necessary.

It is common practice to remove a spinal disc in cases of spinal discdeterioration, disease or spinal injury. More particularly, the discssometimes become diseased or damaged such that the height of the disc isreduced, which causes the annulus to buckle in areas where the laminatedplies are loosely bonded. As the overlapping laminated plies of theannulus begin to buckle and separate, circumferential and/or radialannular tears may occur, allowing nucleus material to escape or form abulge in the annulus. Such disruption to the natural intervertebralseparation and the resulting herniation produces pain, which can bealleviated by removal of the disc and restoration of the naturalseparation distance. In cases of chronic back or leg pain resulting froma degenerated or herniated disc, removal of the disc can become thedesired course of treatment.

In some cases it is desired to fuse the adjacent vertebrae togetherafter removal of the disc. Such a procedure is sometimes referred to as“intervertebral fusion” or “interbody fusion”.

Many techniques and instruments have been devised to performintervertebral fusion. There is common agreement that the strongestintervertebral fusion is interbody fusion between the lumbar bodies,which may be augmented by a posterior or facet fusion. In cases ofintervertebral fusion, either structural bone, or a rigid interbodyfusion “cage” typically filled with morselized bone, is placed centrallywithin the space where the spinal disc once resided. Multiple bonygrafts or cages may be used within that space. Furthermore, multiplesurgical approaches may be utilized, including anterior, posterior, orlateral surgical approaches.

Such practices are characterized by certain disadvantages, including theneed to distract the disc space in order to implant the fusion deviceand thereby restore the diseased disc space to its normal or healthyheight. However, it can be difficult to distract the adjacent vertebralbodies sufficiently to easily insert the fusion device between adjacentvertebral bodies. As a result, it is often necessary to drive the fusiondevice into the space between the vertebral bodies using impaction witha mallet and the application of significant force. The use of suchimpaction and force increases the risk of damage to local soft tissuesuch as blood vessels and the surrounding nerves, and can lead tosuboptimal placement and/or failure of the insertion instrumentation.Furthermore, the use of such impaction and force can damage orcompromise the vertebral endplates, resulting in eventual failure andsubsidence of the fusion device into the vertebral bodies and hence lossof disc height.

Therefore, there is a need for a fusion device that can be placedbetween adjacent vertebral bodies at minimal height and, thereafter, bevariably adjusted with minimal force application to the preferred heightfor an individual patient. Furthermore, it is desirable that theexpandable fusion device be maintained in a closed (i.e., unexpanded)position during insertion and handling, and that it be rigidlyattachable to a holder so as to facilitate maximum control by thesurgeon during insertion and deployment.

SUMMARY

Accordingly, there is now provided an expandable fusion device that canbe placed between adjacent vertebral bodies at minimal height and,thereafter, be variably adjusted with minimal force application to thepreferred height for an individual patient. In one embodiment, anexpandable PLIF (Posterior Lumbar Interbody Fusion) device or anexpandable TLIF (Transforaminal Lumbar Interbody Fusion) device, isdisclosed. The expandable fusion device generally includes: a cage,superior and lower bodys, and an expansion mechanism with opposingproximal and second expansion members. The application of torque to theexpansion mechanism in one direction causes the proximal and secondexpansion members to separate, whereby to move the superior and lowerbodies away from one another and hence increase the height of expandablefusion device 5. The application of torque to the expansion mechanism inthe opposite direction causes the proximal and second expansion membersto approach one another, whereby to move the superior and lower bodystoward one another and hence decrease the height of the expandablefusion device.

Further embodiments may include: (i) angled or lordotic superior andlower bodys to match the angle of the disc space; (ii) mismatchedproximal and second expansion members, such that the anterior portion ofthe expandable fusion device opens more than the posterior portion ofthe expandable fusion device, thereby resulting in a fusion device thatincreases in both height and lordosis; (iii) dual or multiple expansionmechanisms for anterior spinal approaches; (iv) a curved or flexibleholder for the expandable fusion device for oblique access approaches;and (v) additional angled components (i.e., intermediate theaforementioned proximal and second expansion members) for longerexpandable fusion devices.

In some embodiments, system and/or method may include an intervertebralimplant for a human spine including an upper body, a lower body, firstand second expansion members, and an expansion mechanism. The upper bodymay include an inferior surface and a superior surface. The superiorsurface of the upper body may function to engage a first vertebra of thehuman spine. The lower body may include a superior surface and aninferior surface. The inferior surface of the lower body may function toengage a second vertebra of the human spine. The first expansion membermay include at least a first angled portion. The first angled portionmay be positionable, during use, between the inferior surface of theupper body and the superior surface of the lower body. At least thefirst angled portion may be oriented towards a first end of theintervertebral implant. The second expansion member may include at leasta second angled portion positionable, during use, between the inferiorsurface of the upper body and the superior surface of the lower body. Atleast the second angled portion may be oriented towards a second end ofthe intervertebral implant. At least the second angled portion may beoriented in an opposing direction relative to at least the first angledportion. An expansion mechanism may convey, during use, the first andsecond angled portions in opposing directions increasing a separationdistance between the upper body and the lower body. The first and/orsecond angled portion may include a wedge-shaped portion.

In some embodiments, the expansion mechanism may include a threadedelongated member. The threaded elongated member may include a proximallythreaded portion. The first expansion member may include a threadedopening which the threaded portion of the elongated member engages,during use.

In some embodiments, a distal end of the elongated member engages,during use, a proximal end of the second expansion member. The distalend may engage a recess in the second expansion member and rotatesfreely within it.

In some embodiments, the expansion mechanism may include a firstelongated member and a second elongated member. The first elongatedmember may include a proximally threaded portion. The first expansionmember may include a threaded opening which the threaded portion of thefirst elongated member engages, during use. The second elongated membermay be positionable, during use, in an opening in the second expansionmember. A distal end of the first elongated member may engage, duringuse, a proximal end of the second elongated member. In some embodiments,a distal end of the first elongated member may engage, during use, aproximal end of the second elongated member such that the distal end ofthe first elongated member is positioned in the opening in the secondexpansion member.

In some embodiments, the expansion member may include a locking member.The locking member may be positionable in the second expansion membersuch that the distal end of the first elongated member is inhibited,during use, from removal from the opening in the second expansionmember.

In some embodiments, the intervertebral implant may include a cage. Thecage may form a perimeter around the intervertebral implant in which atleast portions of the upper body, the lower body, the first expansionmember, the second expansion member, and the expansion mechanism arepositioned, during use, in the cage. The cage may include one or moreopenings along the perimeter to allow graft material to be positionedduring use.

In some embodiments, a lateral cross section of a perimeter of theintervertebral implant may include a curved shape such that at least afirst portion of the perimeter is substantially convex and at least asecond portion of the perimeter is substantially concave, wherein thesecond portion is substantially opposite the first portion.

In some embodiments, the upper body and/or the lower body may include anopening wherein graft material is positionable during use. The upperbody and/or the lower body may include an opening which increases insize as the first and second angled portions are conveyed in opposingdirections.

In some embodiments, the superior surface of the upper body and/or theinferior surface of the lower body may include protrusions (e.g.,teeth). The protrusions may promote, during use, retention of theimplant between the first vertebra and the second vertebra afterinsertion.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention may become apparent to those skilledin the art with the benefit of the following detailed description of thepreferred embodiments and upon reference to the accompanying drawings.

FIG. 1 depicts a schematic side view showing an expandable fusion deviceformed in accordance with the present invention, with the expandablefusion device being disposed between adjacent vertebral bodies.

FIG. 2 depicts a schematic exploded view of an expandable fusion device.

FIG. 3 depicts a schematic front perspective view of an expandablefusion device, with the expandable fusion device being shown in anunexpanded position.

FIG. 4 depicts a schematic front perspective view of an expandablefusion device, with the expandable fusion device being shown in anexpanded position.

FIG. 5 depicts a schematic rear perspective view of an expandable fusiondevice, with the expandable fusion device being shown in an unexpandedposition.

FIG. 6 depicts a schematic rear perspective view of an expandable fusiondevice, with the expandable fusion device being shown in an expandedposition.

FIG. 7 is a schematic side view of an expandable fusion device, with theexpandable fusion device being shown in an unexpanded position.

FIG. 8 depicts a schematic side view of an expandable fusion device,with the expandable fusion device being shown in an expanded position.

FIG. 9 depicts a schematic top view of an expandable fusion device.

FIG. 10 depicts a schematic side cross-sectional view of an expandablefusion device, with the expandable fusion device being shown in anunexpanded position.

FIG. 11 depicts a schematic side cross-sectional view of an expandablefusion device, with the expandable fusion device being shown in anexpanded position.

FIG. 12 depicts a schematic perspective cross-sectional view of anexpandable fusion device, with the expandable fusion device being shownin an unexpanded condition.

FIG. 13 depicts a schematic perspective view of a lower body.

FIG. 14 depicts a schematic perspective cross-sectional view of a lowerbody.

FIG. 15 depicts a schematic perspective cross-sectional view of an upperbody.

FIG. 16 depicts a schematic right side perspective view of the proximaland second expansion members.

FIG. 17 depicts a schematic left side perspective view of the proximaland second expansion members.

FIG. 18 depicts a schematic view showing insertion instruments for usewith an expandable fusion device.

FIG. 19 depicts a schematic transparent side view of an expandablefusion device.

FIG. 20 depicts a schematic exploded view of an expandable fusiondevice.

FIG. 21 depicts a schematic cross-sectional view of a curved expandablefusion device in an unexpanded state.

FIG. 22 depicts a schematic cross-sectional view of a curved expandablefusion device in an expanded state.

FIG. 23 depicts a schematic view of a curved expandable fusion device asthe device is being inserted between two adjacent vertebrae.

FIG. 24 depicts a schematic view showing insertion instruments for usewith an expandable fusion device.

FIG. 25 depicts a schematic view showing a distal end of an insertioninstrument for use with an expandable fusion device.

FIG. 26 depicts a schematic view showing a proximal end of an insertioninstrument for use with an expandable fusion device.

FIG. 27 depicts a schematic view of a disposable expandable fusionimplant insertion device.

FIG. 28 depicts a schematic transparent view of a disposable expandablefusion implant insertion device.

FIG. 29 depicts a schematic perspective view of an expandable fusionimplant in an expanded state wherein an upper body portion of theimplant is depicted as transparent.

FIG. 30 depicts a schematic perspective view of an expandable fusionimplant in an expanded state wherein an upper body portion of theimplant is depicted as transparent.

FIG. 31 depicts a schematic perspective view of an expandable fusionimplant in a contracted state.

FIG. 32 depicts a schematic perspective view of an expandable fusionimplant in a contracted state coupled to an insertion instrument withportions of the insertion instruments depicted as transparent. An upperbody of the implant is not depicted and a second expandable member isdepicted as transparent.

FIG. 33 depicts a schematic view of an insertion instrument with anexpandable fusion device.

FIG. 34 depicts a schematic view of a distal end of an insertioninstrument with an expandable fusion device.

FIG. 35 depicts a schematic view of a distal end of an insertioninstrument with an expandable fusion device with a portion of theinsertion instrument removed for clarity.

FIG. 36 depicts a schematic view of a distal end of an insertioninstrument with an expandable fusion device with a portion of theinsertion instrument removed for clarity.

FIG. 37 depicts a schematic perspective view of an expandable fusionimplant in a contracted state. At least an upper body and a cage of theimplant is not depicted.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and may herein be described in detail. Thedrawings may not be to scale. It should be understood, however, that thedrawings and detailed description thereto are not intended to limit theinvention to the particular form disclosed, but on the contrary, theintention is to cover all modifications, equivalents and alternativesfalling within the spirit and scope of the present invention as definedby the appended claims.

The headings used herein are for organizational purposes only and arenot meant to be used to limit the scope of the description. As usedthroughout this application, the word “may” is used in a permissivesense (i.e., meaning having the potential to), rather than the mandatorysense (i.e., meaning must). The words “include,” “including,” and“includes” indicate open-ended relationships and therefore meanincluding, but not limited to. Similarly, the words “have,” “having,”and “has” also indicated open-ended relationships, and thus mean having,but not limited to. The terms “first,” “second,” “third,” and so forthas used herein are used as labels for nouns that they precede, and donot imply any type of ordering (e.g., spatial, temporal, logical, etc.)unless such an ordering is otherwise explicitly indicated. For example,a “third die electrically connected to the module substrate” does notpreclude scenarios in which a “fourth die electrically connected to themodule substrate” is connected prior to the third die, unless otherwisespecified. Similarly, a “second” feature does not require that a “first”feature be implemented prior to the “second” feature, unless otherwisespecified.

Various components may be described as “configured to” perform a task ortasks. In such contexts, “configured to” is a broad recitation generallymeaning “having structure that” performs the task or tasks duringoperation. As such, the component can be configured to perform the taskeven when the component is not currently performing that task (e.g., aset of electrical conductors may be configured to electrically connect amodule to another module, even when the two modules are not connected).In some contexts, “configured to” may be a broad recitation of structuregenerally meaning “having circuitry that” performs the task or tasksduring operation. As such, the component can be configured to performthe task even when the component is not currently on. In general, thecircuitry that forms the structure corresponding to “configured to” mayinclude hardware circuits.

Various components may be described as performing a task or tasks, forconvenience in the description. Such descriptions should be interpretedas including the phrase “configured to.” Reciting a component that isconfigured to perform one or more tasks is expressly intended not toinvoke 35 U.S.C. § 112, paragraph six, interpretation for thatcomponent.

The scope of the present disclosure includes any feature or combinationof features disclosed herein (either explicitly or implicitly), or anygeneralization thereof, whether or not it mitigates any or all of theproblems addressed herein. Accordingly, new claims may be formulatedduring prosecution of this application (or an application claimingpriority thereto) to any such combination of features. In particular,with reference to the appended claims, features from dependent claimsmay be combined with those of the independent claims and features fromrespective independent claims may be combined in any appropriate mannerand not merely in the specific combinations enumerated in the appendedclaims.

It is to be understood the present invention is not limited toparticular devices or biological systems, which may, of course, vary. Itis also to be understood that the terminology used herein is for thepurpose of describing particular embodiments only, and is not intendedto be limiting. As used in this specification and the appended claims,the singular forms “a”, “an”, and “the” include singular and pluralreferents unless the content clearly dictates otherwise. Thus, forexample, reference to “a linker” includes one or more linkers.

DETAILED DESCRIPTION

Definitions

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art.

The term “connected” as used herein generally refers to pieces which maybe joined or linked together.

The term “coupled” as used herein generally refers to pieces which maybe used operatively with each other, or joined or linked together, withor without one or more intervening members.

The term “directly” as used herein generally refers to one structure inphysical contact with another structure, or, when used in reference to aprocedure, means that one process effects another process or structurewithout the involvement of an intermediate step or component.

Looking first at FIG. 1, there is shown an intervertebral implant 5(e.g., expandable fusion device) formed in accordance with the presentinvention, with the intervertebral implant 5 being shown disposedbetween a superior vertebral body 10 and an inferior vertebral body 15.As will hereinafter be discussed in further detail, intervertebralimplant 5 may be inserted between superior vertebral body 10 andinferior vertebral body 15 while the intervertebral implant is in acontracted condition (e.g., as depicted in FIGS. 3 and 5), andthereafter expanded (e.g., as depicted in FIGS. 4 and 6) as necessary soas to span and engage the endplate 20 of superior vertebral body 10 andthe endplate 25 of inferior vertebral body 15, whereby to supportsuperior vertebral body 10 and inferior vertebral body 15 relative toone another.

In some embodiments, (e.g., as depicted in FIG. 2) intervertebralimplant 5 (e.g., as depicted in FIG. 2) generally includes a cage 30, anupper body 35, a lower body 40, an expansion mechanism 45, a firstexpansion member 50 (e.g., positioned proximally) and a second expansionmember 55 (e.g., positioned distally). As will hereinafter be discussed,the application of torque to expansion mechanism 45 in one directioncauses first expansion member 50 and second expansion member 55 toseparate, whereby to move upper body 35 and lower body 40 away from oneanother and hence increase the height of intervertebral implant 5. Theapplication of torque to expansion mechanism 45 in the oppositedirection causes first expansion member 50 and second expansion member55 to draw towards one another, whereby to move upper body 35 and lowerbody 40 toward one another and hence decrease the height ofintervertebral implant 5. In some embodiments, the mechanism may bereversed with, for example, the expansion members moving towards oneanother during expansion (although the opening for biological materialmight be reduced in such an embodiment).

Designs which may be similar but with for example expansion membersconveying in the same direction may have a mechanical disadvantagerelative to the embodiments described herein wherein the expansionmembers are conveyed in opposing directions. Expansion members which areconveyed in opposing directions may require half of the input torque tomove as opposed to expansion members which are conveyed in the samedirection.

In some embodiments, a cage 30 includes a generally rectangularstructure 60 having a hollow interior 65, a distal opening 70 and aproximal opening 75. Two seats 80 are formed in the opposing sidesurfaces of cage 30.

Upper body 35 generally includes a block 85 having an inferior recess90, and a textured superior surface 95, and a pair of inclined cammingsurfaces 100, 105. Camming surfaces 100, 105 of upper body 35 may beinclined in opposite directions (e.g., as depicted in FIG. 15).

Lower body 40 generally includes a block 110 having a superior recess115, a textured inferior surface 120 and a pair of inclined cammingsurfaces 125, 130. Camming surfaces 125, 130 of lower body 40 may beinclined in opposite directions (e.g., as depicted in FIGS. 13-14).

In some embodiments, the camming surface 100 of upper body 35 and thecamming surfaces 130 of lower body 40 extend parallel to one another,and the camming surfaces 105 of upper body 35 and the camming surface125 of lower body 40 extend parallel to one another.

Expansion mechanism 45 generally includes an elongated shaft 135 havingan annular shoulder 140 formed intermediate its length. A groove 145 isformed distal to annular shoulder 140. Screw threads 147 are formed onthe outer surface of elongated shaft 135 proximal to annular shoulder140. A noncircular bore 150 opens on the proximal end of expansionmechanism 45 and extends distally thereof.

Superior and/or inferior surfaces of the implant (e.g., texturedsuperior surface 95 and textured inferior surface 120) may includevarious features to facilitate engagement of the surfaces with endplatesof adjacent vertebrae. In some embodiments, the implant may include aplurality of surface deformations positioned on the inferior surfaceand/or the superior surface. Surface deformations may includeprotrusions. For example (e.g., depicted in FIG. 7) superior surface ofthe implant 5 may include protrusions (e.g., teeth) 154 extending therefrom. During use, teeth 154 may extend/penetrate into adjacent boneystructure of the upper and lower adjacent vertebrae. Such penetrationmay help to fix a position of the implant 5 relative to the vertebrae.Fixing or otherwise stabilizing the implant may reduce the likelihood ofimplant 5 being expelled from within the intervertebral space, and maypromote bone attachment to and through implant 5. In some embodiments,various spray coatings may be applied to one or more exterior surfacesto, for example, enhance fixation with adjacent bone surfaces.

In some embodiments, protrusions 154 may include directional teeth thatfacilitate movement of the members in a first direction, but inhibitmovement of the members in a second opposing direction. For example, inthe illustrated embodiment, teeth 154 include a ramped leading surface154 a and a substantially vertical trailing edge 154 b (e.g., depictedin FIGS. 7-8). Thus, forward advancement of the members may befacilitated as boney structure of the vertebrae slides over rampedleading surface 154 a of teeth 154 and backward advancement may beinhibited by substantially vertical trailing edge 154 b hooking into orotherwise engaging the boney structure of the vertebrae.

In some embodiments, one or more portions of the implant may include oneor more markers. Markers may be used to assess a position of one or moreportions of the implant during implantation in a subject. A portion ofthe implant may include none, one or multiple markers. Markers mayprovide radiographic opacity. Markers may be biocompatible. Markers maybe of any size or shape. In some embodiments, a system may have multiplemarkers with different shapes in order to more easily identify differentportions or directions of the system and/or an orientation of one ormore portions of the implant. In some embodiments, one or more markersmay be formed from gold or tantalum.

In some embodiments, the implant 5 may include an opening 152 aextending through the implant (e.g., depicted in FIGS. 9-12). Theopening may hold biological material during use. In some embodiments,opening 152 a may be filled with a substance/material to facilitate bonegrowth/fusion. Once implant 5 is implanted, the opening may facilitate acolumn of bone growth between the adjacent vertebrae through the opening152 a. In some embodiments, an opening (e.g., opening 152 a) mayfunction as a graft window containing bone chips and/or materials whichfacilitate tissue (e.g., bone) growth. The opening may increase in sizeas the first and second expansion members move away from each other asthe implant is deployed.

In some embodiments, implant 5 may include one or more second openings152 b (e.g., depicted in FIG. 20). The second openings may be positionedon either side of cage 30. The openings may facilitate insertion ofbiological material. After positioning an implant during use opening 152a may be blocked by the vertebrae and therefore additional openings 152b may facilitate in packing of biological material (e.g., bone graft).The openings may be initially at least partially blocked by the firstand second expansion members and/or the upper and lower bodies, as theimplant is expanded the second openings may open up.

In some embodiments, implant 5 may include a proximal opening 152 c(e.g., depicted in FIG. 29). A proximal opening may allow biologicalmaterial to be positioned in the interior of the implant after theimplant has been positioned. The proximal opening may facilitateinsertion of biological material after insertion of the implant. In someembodiments, a proximal opening in the implant may necessitatepositioning the expansion mechanism (e.g., elongated members 45 a-b asdepicted in FIGS. 30-31) off center in order to allow for creating alarge enough proximal opening. In some embodiments, the first expansionmember 50 may be modified to allow biological material inserted throughthe proximal opening to pass beyond the first expansion member into thespace between the first and the second expansion member 50, 55. Thefirst expansion member may include an opening 156 and/or shaped tocreate an opening in combination with an interior surface of the cage 30(e.g., as depicted in FIGS. 32 and 37).

In some embodiments, a distal end 235 of the elongated member (e.g.,expansion mechanism 45 a) engages, during use, a proximal end of thesecond expansion member 55. In such an embodiment, the distal end of theelongated member abuts a proximal end of the second expansion member asopposed to extending through an opening in the second expansion member.The distal end may engage a recess 240 in the second expansion member 55(e.g., as depicted in FIG. 19). A recess may include a shallow opening.The distal end may turn freely in the recess. The recess may assist incentering and/or positioning the distal end of the elongated member 45such that the distal end is inhibited from misaligning and/ordisengaging from the second expansion member. In some embodiments, theimplant 5 may include a second elongated member 45 b. The secondelongated member 45 b may be positioned in the second expansion member55 and opening 70 such that the second elongated member keeps the secondexpansion member centered.

In some embodiments, the expansion mechanism may include a firstelongated member 45 a and a second elongated member 45 b (e.g., asdepicted in FIG. 20). The first elongated member 45 a may include aproximally threaded portion 147. The first expansion member 50 mayinclude a threaded opening 180 which the threaded portion of the firstelongated member engages, during use. The second elongated member 45 bmay be positionable, during use, in an opening 210 in the secondexpansion member 55. A distal end 245 of the first elongated member 45 amay engage, during use, a proximal end 250 of the second elongatedmember 45 b. In some embodiments, a distal end of the first elongatedmember may engage, during use, a proximal end of the second elongatedmember such that the distal end of the first elongated member ispositioned in the opening in the second expansion member. The distal endof the first elongated member may turn freely in the opening in thesecond expansion member. In some embodiments, the second elongatedmember may function to keep the second expansion member 55 central inthe body of the implant. In some embodiments, the second elongatedmember may be essentially non-rotating relative to the first elongatedmember.

The result is that the separation between the expansion members is thusequal to just one pitch of the thread per rotation, or ½ pitch ofmovement relative to the endplate (upper & lower body) each. As such fora given torque one may provide approximately twice the lifting force ascompared to dual expansion members moving in the same direction at 1pitch per rotation. Embodiments discussed herein would have twice theseparation force relative to a turnbuckle thread configured withopposing expansion members (or even with expansion members moving in thesame direction) because they separate/collapse at a rate of 2 pitchesper rotation and thus have twice the motion relative to the endplates.

In some embodiments, a size of the expansion member (e.g., screw) may bereduced to get the same force at a lower torque because passive rotationwithin one of the expansion members is more efficient. One may reducethe angle of the ramp or have a single ramp, but you would needconsiderably more travel to achieve the same height and would run intolength limitations. Many embodiments described herein increase rotationsnot travel.

Forming the expansion mechanism from two elongated members as opposed toa single elongated member has several advantages. For example whenretracting upper body 35 and lower body 40 from an engaged position toan unengaged position, torque applied to the expansion mechanism duringretraction may lead to failure of the expansion mechanism when theexpansion mechanism includes a single elongated member. When theexpansion mechanism includes two elongated members, failure of theexpansion mechanism when counter (retracting) torque is applied isinhibited.

In some embodiments, one or more of the expansion members may include alocking member 255. The locking member may be positionable in the secondexpansion member 55 such that the second elongated member is inhibited,during use, from removal from the opening in the second expansionmember. The locking member may include a pin. The pin may be positionedin an opening in the second expansion member. In some embodiments, thelocking member may engage a recess 260 in the second elongated member.The recess may circumscribe the circumference of the second elongatedmember such that the second elongated member does not have to beoriented in a particular direction relative to the second elongatedmember. In some embodiments, the locking member may be used incombination with the single elongated member (e.g., snap ring 215 asdepicted in FIG. 2).

In some embodiments, first expansion member 50 includes a generallywedge-shaped body 155 having a superior camming surface 160, an inferiorcam surface 165, a pair of superior fingers 170 and a pair of inferiorfingers 175 (e.g., as depicted in FIG. 16). Significantly, superiorcamming surface 160 of first expansion member 50 extends parallel tocamming surface 100 of upper body 35, and inferior camming surface 165of first expansion member 50 extends parallel to camming surface 125 oflower body 40. In lordotic embodiments these surfaces may only beparallel in the open position. They are not parallel when closed. Firstexpansion member 50 may include a threaded bore 180 extending therethrough. Threaded bore 180 is sized to be threadingly engaged by screwthreads 147 on elongated shaft 135.

In some embodiments, second expansion member 55 includes a generallywedge-shaped body 185 having a superior camming surface 190, an inferiorcamming surface 195, a pair of superior fingers 200 and a pair ofinferior fingers 205 (e.g., as depicted in FIGS. 16-17). Significantly,superior camming surface 190 of second expansion member 55 extendsparallel to camming surface 105 of upper body 35, and inferior cammingsurface 195 of second expansion member 55 extends parallel to cammingsurface 130 of lower body 40. In lordotic embodiments these surfaces mayonly be parallel in the open position. They are not parallel whenclosed. Second expansion member 55 may include a smooth bore 210extending there through. Smooth bore 210 may be sized to receive theportion of expansion mechanism 45 distal to annular shoulder 140.

Camming surfaces of the upper/lower bodies and the expansion members maybe substantially flat as depicted in some of the attached FIGS. In someembodiments, at least some of the camming surfaces may be curved.Complementary camming surfaces may be complementarily shaped.Complementary camming surfaces may not be complementarily shaped.

In some embodiments, intervertebral implant 5 may be assembled so thatexpansion mechanism 45 extends through proximal opening 75 in cage 30(without engaging proximal opening 75 in cage 30), and first expansionmember 50 and second expansion member 55 are disposed on shaft 135 ofexpansion mechanism 45 within the hollow interior 65 of cage 30. Moreparticularly, first expansion member 50 may be mounted on elongatedshaft 135 of expansion mechanism 45 so that screw threads 147 arethreadingly received in threaded bore 180 of first expansion member 50,and second expansion member 55 is mounted on elongated shaft 135 ofexpansion mechanism 45 so that second expansion member 55 is captured onelongated shaft 135 between annular shoulder 140 and a snap ring 215secured in groove 145. At the same time, upper body 35 and lower body 40may extend into hollow interior 65 of exterior body 30 so that (i)camming surface 100 of upper body 35 rides on camming surface 160 offirst expansion member 50, (ii) camming surface 105 of upper body 35rides on camming surface 190 of second expansion member 55, (iii)camming surface 125 of lower body 40 rides on camming surface 165 offirst expansion member 50, and (iv) camming surface 130 of lower body 40rides on camming surface 195 of second expansion member 55.

It will be appreciated that, as a result of the foregoing construction,the application of torque to expansion mechanism 45 in one direction(e.g., in a noncircular bore 150 in expansion mechanism 45) causes firstexpansion member 50 and second expansion member 55 to separate, wherebyto move upper body 35 and lower body 40 apart and hence increase theheight of intervertebral implant 5. It will be appreciated that, as aresult of the foregoing construction, the application of torque toexpansion mechanism 45 in the opposite direction causes first expansionmember 50 and second expansion member 55 to draw together, whereby tomove upper body 35 and lower body 40 together and hence decrease theheight of intervertebral implant 5.

In some embodiments, the intervertebral implant 5 may include a curvedcross-section. Straight designs are more commonly associated with PLIF(direct posterior placement in pairs), or lateral approaches (one longerdevice placed from the side of the spine). FIG. 21 is a schematiccross-sectional view of a curved expandable fusion device in anunexpanded state with a curved cross-section. FIG. 22 is a schematiccross-sectional view of a curved expandable fusion device in an expandedstate with a curved cross-section. In some embodiments, portions of theimplant may be curved or angled in order to accommodate the curvedcross-section of the perimeter. In some embodiments, expansion membersand the expansion mechanism may not require adjustments to assimilateinto an implant with a curved perimeter. The distal end 235 of theexpansion mechanism 45 a may engage a recess 240 in the second expansionmember 55 as discussed herein and in the case of a curved implant therecess may adjusted to compensate for the varying angle of engagement ofthe distal end with the recess during expansion. In some embodiments,the distal end of the expansion mechanism may be curved in order toaccommodate a curved perimeter.

The reason TLIF cages are typically curved is that the surgicaltechnique would be to place them from a posterior-lateral approach, asmuch as 45 degrees off the midline, where they are tamped and rotated tothe front of the vertebral body. A curved implant may facilitateinsertion of the implant between adjacent vertebrae. An implant with acurved perimeter may better mimic and accommodate the existing perimeterof the average vertebra. FIG. 23 depicts a schematic view of a curvedexpandable fusion device 5 as the device is being inserted between twoadjacent vertebrae. In some embodiments, the implant inserter may becurved. The expansion mechanism may have a flexible shaft to allowrotation within the curve. The relative advantages of an expandablefeature may in fact be greater because it would significantly reduce theimpaction required to maneuver the device into final position at thefront of the spine.

In some embodiments, an implant system may include an implant insertiondevice 300. FIG. 18 shows a handle 215, a holder 220 and an engagingmember 225 which may be used to manipulate and deploy intervertebralimplant 5. More particularly, handle 215 includes two extensions 230 forpositioning in seats 80 (e.g., as depicted in FIGS. 3-6) ofintervertebral implant 5. Holder 220 may be positionable in handle 215and threadingly engages the distal end of expansion mechanism 45,whereby to releasably secure intervertebral implant 5 to handle 215.Engaging member 225 may be positionable in holder 220 and into bore 150in expansion mechanism 45, whereby to permit the user to turn expansionmechanism 45 and hence adjust the height of the intervertebral implant5. Engaging member 225 may include engaging head 226 which engages bore150. Engaging head 226 may include a complementary shape to bore 150such that as the head turns the expansion member 45 turns.

In some embodiments, an implant system may include an implant insertiondevice 300. FIGS. 24-26 depict a schematic view showing insertioninstruments 300 for use with an expandable fusion device. FIGS. 24-26depict a handle 215, a holder 220 and an engaging member 225 which maybe used to manipulate and deploy intervertebral implant 5. Moreparticularly, handle 215 includes two extensions 230 for positioning inseats 80 (e.g., as depicted in FIGS. 24-25) of intervertebral implant 5.Engaging member 225 may be positionable in holder 220 and into bore 150in expansion mechanism 45, whereby to permit the user to turn expansionmechanism 45 and hence adjust the height of the intervertebral implant5. Engaging member 225 may include engaging head 226 which engages bore150. Engaging head 226 may include a complementary shape to bore 150such that as the head turns the expansion member 45 turns. In someembodiments, the insertion instrument 300 may include a grip 280 coupledto engaging member 225. In some embodiments, engaging member 225 mayinclude a threaded proximal portion 285. The threaded portion 285 mayfunction to assist in controlling longitudinal movement of the engagingmember and therefore expansion of the implant.

In some embodiments, an insertion device may be disposable. FIGS. 27-28depict a schematic view of a disposable expandable fusion implantinsertion device 300. A disposable insertion device may be packaged withan implant. The insertion device may allow bone graft to be packed afterinsertion. The “disposable” option may allow the holder to act as aninternal funnel which would make cleaning difficult, but a “durableversion” remains an option. In some embodiments, engaging member 225 maybe used to pack biological material into the implant through holder 220.In some embodiments, a separate packing instrument (not depicted) may beused to insert biological material.

FIGS. 32-36 depict a schematic view showing insertion instruments 300for use with an expandable fusion device. FIGS. 32-36 depict a handle215, a holder 220 and an engaging member 225 which may be used tomanipulate and deploy intervertebral implant 5. More particularly,handle 215 includes two extensions 230 for positioning in seats 80(e.g., as depicted in FIGS. 24-25) of intervertebral implant 5. In someembodiments, the extensions may be spring loaded (e.g., using springs,forming at least a portion of the extensions from an at least slightlyflexible material, etc.) such that they are biased to be positioned suchthat they apply pressure to the seats of the implant during use. In someembodiments, a mechanism may be employed to engage/release theextensions from the implant.

The insertion instrument may include at least two holders 220 whichcouple to opposing sides (e.g., the inferior and superior surfaces ofthe implant) of the implant during use. In some embodiments, the holdersmay be spring loaded (e.g., using springs, forming at least a portion ofthe holders from an at least slightly flexible material, etc.) such thatthey are biased to be positioned such that they apply pressure to thesurfaces of the implant during use. In some embodiments, a mechanism maybe employed to engage/release the holders from the implant. The holdersmay include a curved edge or lip which curve towards one another. Thecurved edge may engage an appropriately shaped portion of the proximalend of the implant.

Engaging member 225 may be positionable in handle 215 and into bore 150in expansion mechanism 45, whereby to permit the user to turn expansionmechanism 45 and hence adjust the height of the intervertebral implant5. Engaging member 225 may include engaging head 226 which engages bore150. Engaging head 226 may include a complementary shape to bore 150such that as the head turns the expansion member 45 turns. In someembodiments, the insertion instrument 300 may include a grip 280 coupledto engaging member 225.

In this patent, certain U.S. patents, U.S. patent applications, andother materials (e.g., articles) have been incorporated by reference.The text of such U.S. patents, U.S. patent applications, and othermaterials is, however, only incorporated by reference to the extent thatno conflict exists between such text and the other statements anddrawings set forth herein. In the event of such conflict, then any suchconflicting text in such incorporated by reference U.S. patents, U.S.patent applications, and other materials is specifically notincorporated by reference in this patent.

Further modifications and alternative embodiments of various aspects ofthe invention will be apparent to those skilled in the art in view ofthis description. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the invention. It is to beunderstood that the forms of the invention shown and described hereinare to be taken as the presently preferred embodiments. Elements andmaterials may be substituted for those illustrated and described herein,parts and processes may be reversed, and certain features of theinvention may be utilized independently, all as would be apparent to oneskilled in the art after having the benefit of this description of theinvention. Changes may be made in the elements described herein withoutdeparting from the spirit and scope of the invention as described in thefollowing claims.

What is claimed is:
 1. A method for increasing the spacing between twoadjacent vertebral bodies, the method comprising: removing at least aportion of a disc between two vertebrae of the human spine to create aspace between the two vertebrae; positioning an intervertebral implantin the space between the two vertebrae, wherein the intervertebralimplant comprises: a cage comprising a first end portion, a second endportion, a longitudinal axis extending between the first end portion andthe second end portion, an upper portion and a lower portion; an upperbody movably mounted to the cage, the upper body comprising an inferiorsurface and a superior surface; a lower body movably mounted to thecage, the lower body comprising a superior surface and an inferiorsurface; a first expansion member comprising at least a first inclinedportion, wherein at least the first inclined portion is oriented towardsthe first end portion of the cage; a second expansion member comprisingat least a second inclined portion, wherein at least the second inclinedportion is oriented towards the second end portion of the cage; and anexpansion mechanism movably mounted to the cage, wherein the expansionmechanism comprises a threaded portion for threadingly engaging athreaded portion of the first expansion member, and further wherein thesecond expansion member is non-threadingly coupled to the expansionmechanism, such that when the expansion mechanism is rotated, theexpansion mechanism moves relative to the cage, the first expansionmember is moved relative to the cage and relative to the expansionmechanism, and the second expansion member is moved relative to the cagein the opposing direction, so as to increase a separation distancebetween the upper body and the lower body; and rotating the expansionmechanism so as to move the first and second expansion members inopposing directions so as to increase a separation distance between theupper body and the lower body.
 2. The method of claim 1; furthercomprising engaging a first vertebra of the human spine using thesuperior surface of the upper body.
 3. The method of claim 2, whereinthe superior surface of the upper body comprises teeth for engaging thefirst vertebra.
 4. The method of claim 1, further comprising engaging asecond vertebra of the human spine using the inferior surface of thelower body.
 5. The method of claim 4, wherein the inferior surface ofthe lower body comprises teeth for engaging the second vertebra.
 6. Themethod of claim 1, wherein, when the expansion mechanism is rotated, thefirst inclined portion of the first expansion member moves towards thefirst end portion of the cage and the second inclined portion of thesecond expansion member moves towards the second end portion of thecage.
 7. The method of claim 1, wherein, when the expansion mechanism isrotated, one of the first expansion member and the second expansionmember moves a further distance relative to the cage than the other ofthe first expansion member and the second expansion member.
 8. Themethod of claim 1, wherein, before rotation of the expansion mechanism,the superior surface of the upper body and the inferior surface of thelower body are parallel to the longitudinal axis of the cage.
 9. Themethod of claim 1, wherein, before rotation of the expansion mechanism,the superior surface of the upper body and the inferior surface of thelower body are both inclined relative to the longitudinal axis of thecage.
 10. The method of claim 1, wherein, after rotation of theexpansion mechanism, the superior surface of the upper body and theinferior surface of the lower body are parallel to the longitudinal axisof the cage.
 11. The method of claim 1, wherein; after rotation of theexpansion mechanism, the superior surface of the upper body and theinferior surface of the lower body are both inclined relative to thelongitudinal axis of the cage.
 12. The method of claim 1, wherein thefirst inclined portion of the first expansion member comprises a flatsurface.
 13. The method of claim 1, wherein the second inclined portionof the second expansion member comprises a flat surface.
 14. The methodof claim 1, wherein the first inclined portion of the first expansionmember comprises a curved surface.
 15. The method of claim 1, whereinthe second inclined portion of the second expansion member comprises acurved surface.
 16. The method of claim 1 wherein the first inclinedportion of the first expansion member comprises a first geometry, thesecond inclined portion of the second expansion member comprises asecond geometry, and further wherein the first geometry is differentfrom the second geometry.
 17. The method of claim 1, wherein the cageforms a perimeter for the intervertebral implant, and further wherein atleast portions of the upper body, the lower body, the first expansionmember, the second expansion member, and the expansion mechanism arepositioned within the perimeter.
 18. The method of claim 17, wherein thecage comprises a curved shape such that a first portion of the perimeteris substantially convex and a second portion of the perimeter issubstantially concave, wherein the second portion is substantiallyopposite the first portion.
 19. The method of claim 17, wherein the cagecomprises one or more openings along the perimeter to allow graftmaterial to be positioned during use.
 20. The method of claim 1, whereinat least one of the upper body and the lower body comprises an openingwithin which graft material is positionable during use.
 21. The methodof claim 1, wherein the upper body and the lower body define an openingtherebetween, and further wherein this opening increases in size as thefirst and second inclined portions of the first and second expansionmembers, respectively, are moved.